Multipair phase-modulated temporal interference electrical stimulation combined with fMRI

Temporal interference stimulation (TIS) is a non-invasive brain stimulation technique that exploits frequency-shifted kHz fields to modulate oscillatory neural activity. While human studies suggest TIS efficacy in targeting relatively deep brain structures, recent computational modeling and animal studies indicate potential off-target stimulations via standard TIS protocols. Here, we computationally optimized TIS targeting for the medial prefrontal cortex (mPFC) in mice. Combining in vivo electrophysiological recordings, intracellular calcium dynamics with fiber photometry, and functional MRI, we confirmed TIS-induced amplitude modulation, neuronal entrainment, and hemodynamic responses in the mPFC, while also identifying off-target modulations. To mitigate off-target effects, we introduced a configuration with three electrode pairs, one of which is actively phase-shifted by 180°. This canceling field enhanced TIS focality, thereby reducing off-target effects without compromising TIS efficacy in the target area. This work effectively addresses one of TIS's most critical shortcomings and opens new avenues for research and clinical applications. A record of this paper's transparent peer review process is included in the supplemental information.